Present embodiments relate to a gas turbine engine having a fuel nozzle within a combustor that discharges hot gasses into a high pressure turbine. More particularly, the present embodiments include those that relate to combustion gas hot streaks which are aligned in a circumferential direction with every other first stage nozzle vane and which allow for less cooling air usage at non-aligned vanes.
In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor having a fuel nozzle thereby generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. Flowise, the hot gasses enter a high pressure turbine which includes a first stage stator nozzle and a rotor assembly including a disk and a plurality of turbine blades. In further detail, the high pressure turbine first receives the hot combustion gasses from the combustor at the first stage stator nozzle that directs the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a first rotor disk. In a two stage turbine, a second stage stator nozzle is positioned downstream of the first stage blades followed in turn by a row of second stage turbine blades extending radially outwardly from a second rotor disk. The stator nozzles turn the hot combustion gas in a manner to maximize extraction at the adjacent downstream turbine blades.
The first and second rotor disks are joined to the compressor by a corresponding rotor shaft for powering the compressor during operation. The turbine engine may include a number of stages stators and rotors wherein static airfoils, commonly referred to as vanes, are interspaced an axial direction in the engine between rotating airfoils commonly referred to as blades. A multi-stage low pressure turbine follows the two stage high pressure turbine and is typically joined by a second shaft to a fan disposed upstream from the compressor in a typical turbofan aircraft engine configuration for powering an aircraft in flight.
As the combustion gasses flow downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced. The combustion gas is used to power a turbine output shaft for power and marine use or provide thrust in aviation usage.
More specifically, a combustor includes any number of combustor fuel nozzles which deliver fuel and facilitate mixing a method of compressed air to achieve a stable flame in the combustor chamber. At the combustor exit where combustion gas exits, a temperature profile will indicate that there are hotter and colder zones. The hotter zones are commonly referred to as hot streaks. Hot streaks are typically randomly arranged about a combustor relative to the first stage high pressure turbine nozzles. However aiming of hot streaks may occur for integer ratios of fuel nozzles and stator vanes. In such an arrangement, hot streaks may be aimed at open areas of nozzle segments between the vanes so as to limit damage on the material forming the nozzle structures. Such damage may include oxidation, thermo-mechanical fatigue and a commensurate reduction in durability. This reduction in durability leads to increased replacement intervals which come at a high cost to turbine engine operators.
Some engines include the stator nozzle assembly being, for example, an annular ring formed as a single piece. Other engines include the turbine stator nozzle assembly being formed as an annulus by a plurality of stator nozzle segments arranged in an annular array. The nozzle segments each include an inner band, an outer band and a vane extending therebetween. The vanes are hollow and receive a portion of pressurized air from the compressor which is used for cooling the vanes during operation.
There are two problems with the current state of the art. First, in allowing the hot streak to pass between vanes unimpeded, the hot streak will reach components downstream of the first stage stator nozzle with only limited mixing with air provided for turbine cooling. This can lead to damage of the downstream components. Second, present designs do not address issues with cooling air, specifically the continual desire to reduce the cooling air usage or control losses due to cooling air use in a turbine engine.
As may be seen in the foregoing section, there is a need for design improved mixing of hot streak gases while limiting damage to downstream components of the first stage nozzle. Additionally, a need exists to increase durability of the turbine components including the first stage stator nozzle and turbine blades as well as for embodiments including multiple-stage assemblies.
In the past, an unmet need has also been to decrease the usage of cooling gas at vanes which are not directly impinged by any hot streak so that some portion of such cooling air may be utilized to improve minor emissions or other beneficial functionality of the gas turbine engine. The present embodiments address all these needs and more.